It's not as much giving up on a full C, as the standards increasing and it not beign worth the cost to upgrade. Prior to the C1 and C2 designation, anything in this region over 6kW at 100 meters (or equivalent) was class C. Then the bar was set at 100 kW at 300 meters (just shy of 1000 feet). When the C0 class was added, the bar moved up to 450 meters. Any station that is below their classification keeps it, until another station files to "downgrade" it to the conforming class.
Building a tall tower is not cheap or easy, especially in a metro area. Permits, NIMBY, FAA, etc. The coverage difference between 300 and 600 meters is most noticeable on the fringes, so you're talking about the listeners who are 50-70 miles out. A lot of stations did build out in the mid to late 80's, especially those on very short sticks. FM had become the dominant medium by then, so there was good reason to spend the money and end u with a competitive signal.
The difference between 100kW at 300 meters and at 450 meters is pretty negligible, especially within the closer reaches. So unless there's a tall tower very close by (most stations are pretty hemmed in now) or there's an opportunity to "move in" to a metro market as a "rim shot," it really isn't worth the cost. Some stations will put the process on hold for a few years by filing for a CP at an acceptable height and eventually letting it expire (by choice or by economic circumstance).
Building a tall tower is not cheap or easy, especially in a metro area. Permits, NIMBY, FAA, etc. The coverage difference between 300 and 600 meters is most noticeable on the fringes, so you're talking about the listeners who are 50-70 miles out. A lot of stations did build out in the mid to late 80's, especially those on very short sticks. FM had become the dominant medium by then, so there was good reason to spend the money and end u with a competitive signal.
The difference between 100kW at 300 meters and at 450 meters is pretty negligible, especially within the closer reaches. So unless there's a tall tower very close by (most stations are pretty hemmed in now) or there's an opportunity to "move in" to a metro market as a "rim shot," it really isn't worth the cost. Some stations will put the process on hold for a few years by filing for a CP at an acceptable height and eventually letting it expire (by choice or by economic circumstance).